1. Field of the Invention
This invention relates to reciprocating equipment along a work path, and more particularly to a reel providing a drum having one surface which is shared by a single layer of a take up cable and by a pay out cable during reciprocation of the equipment in a clarifier basin for collecting sludge.
2. Discussion of Prior Art
In the past, clarifier basins have been provided with sediment collecting devices that move on a track fixed to the floor of the basin. In one such device, patented by Applicant in U.S. Pat. No. 4,401,576, a carriage is provided for movement along the track. The carriage is moved by a stepping mechanism that grips the track and moves the carriage relative to the track. Although such stepping mechanism has been commercially successful, mechanisms that are located under the water are inherently difficult to maintain because the track is located under water where sediment or sludge collects on the floor of the clarifier basin.
In other devices for removing sludge from the floor of clarifier basins, floats are pulled alternately in opposite directions across the surface of the clarifier basin. Pipes extend from the floats to the floor for sludge collection. The floats are pulled by a cable which has first and second ends. The first cable end is wound in one direction on a winch and the second cable end is wound in an opposite direction on the winch, such that rotation of the winch in one direction unwinds (pays out) the first end of the cable and winds up (takes up) such second end of the cable to pull the float in one direction across the basin. Reversing the direction of rotation of the winch reverses the direction in which the float is pulled across the basin. In a device of this type disclosed in U.S. Pat. No. 3,416,176 issued in 1968, the winch has a fixed diameter drum. Both the first and the second ends of the cable are tightly wound on the drum of the winch. In this device, if the travel of the float is long enough to require the cables to wind on themselves and form more than one layer on the drum, the length of cable unwound from the now-larger diameter on the drum will exceed that wound directly on the drum. To compensate for the unequal diameters and the resulting unequal lengths taken up and payed out, one requires use of spring-biased pulleys, for example.
In other drives for reciprocating devices along a path, one end of a cable is wound in one direction on a drum and the other end of the cable is wound in the other direction on the drum. In one such unit disclosed in U.S. Pat. No. 630,962 issued in 1899, the drum is provided with three surfaces, the outer two of which surfaces are conical in shape for receiving a pair of cables that are wound in a first direction. The other surface, a central cylindrical drum, receives a sounding line that is wound in a direction opposite to that of the cables. This unit requires the use of cable guides that are provided on a lead screw for guiding the cables onto selected and controlled portions of the conical surfaces.
In the art of moving or lifting objects, the single drum of an ordinary hoist has been provided with a ring that divides the single drum into two sections. In one such apparatus disclosed in U.S. Pat. No. 747,113 issued in 1903, a button has been provided on such ring and is used for engaging a rope so that as both sections of the drum are rotated in the same direction, one section of the drum winds up one length of the rope on one section of the drum, while another length of the rope unwinds from the other section of the drum.
In other drives for positioning transducers along a longitudinal path, such as disclosed in U.S. Pat. No. 4,198,871 issued in 1980, a capstan is driven by a stepper motor through a maximum angle of 180 degrees in either of two directions. The capstan is provided with a cylindrical surface to which opposite ends of a flexible, steel belt are secured at separate, axially spaced locations on the capstan. Those ends of the belt are wrapped in opposite directions on the capstan. In practice the rotation of the capstan is limited to 135 degrees as the rotation of the capstan in one direction unwinds one end of the belt from its separate location on the capstan, and winds up the other end of the belt at its separate axial location on the capstan. Because of the limited rotation of the capstan, each of the separate belt ends does not wrap onto itself as it is wrapped on the capstan. Because of the separate axial locations of the belt ends, combined with such limited amount of rotation, each separate belt end does not wrap on the capstan to the location of the other belt end.
In a high speed printer disclosed in U.S. Pat. No. 3,872,960 issued in 1975, a motor drives a helically grooved pulley which has attached to it left and right cable segments of equal length. The other ends of the cable segments are attached to a movable carriage. One pulley of this system is spring biased to remove from either of the cables any slack which might occur due to long-term temperature drift.